WEBVTT - Is There A Noise Loud Enough To Kill You?

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<v Speaker 1>Welcome to brain stuff from how stuff works. Hey, I'm

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<v Speaker 1>Christian Sager and this is brain stuff. If you're standing

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<v Speaker 1>next to a jet during takeoff, your ear drums will

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<v Speaker 1>probably burst. Same thing happens when you fire a twelve

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<v Speaker 1>gage shotgun right next to your ear. When we're exposed

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<v Speaker 1>to exceptionally loud noises, something called the stereocilia in our

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<v Speaker 1>ears gets damaged. This causes our ears to mistakenly send

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<v Speaker 1>signals to our auditory nerve cells. The resulting ghostly reverberations

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<v Speaker 1>are what we call ringing ear. Many of you have

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<v Speaker 1>probably experienced this, possibly from going to a really loud concert.

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<v Speaker 1>The technical term for it is tenitus, and it's usually

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<v Speaker 1>temporary unless you repeatedly damage your ears with loud noises.

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<v Speaker 1>Then it develops into chronic tenitis, where you hear that

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<v Speaker 1>dull ringing for the rest of your life. And that's

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<v Speaker 1>nothing compared what really loud noise can do to you.

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<v Speaker 1>Noise hates you, and noise can kill you. See. Sound

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<v Speaker 1>travels in waves that enter our ear canals. These waves

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<v Speaker 1>make our ear drums vibrate, and if they're too strong,

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<v Speaker 1>they can snap the hair cells inside. And if these

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<v Speaker 1>hair cells die they can never grow back. To avoid this,

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<v Speaker 1>we use units called decibels to measure the power of sound.

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<v Speaker 1>Anything below eighty five decibels is thought to be safe.

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<v Speaker 1>At a hundred and fifty decibels, your ear drums burst

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<v Speaker 1>like with the jet or the shotgun, and at two

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<v Speaker 1>hundred decibels, your lungs will rupture and likely kill you.

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<v Speaker 1>That's right. The threshold for death by sound is somewhere

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<v Speaker 1>between a hundred and eighty five and two hundred decibels.

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<v Speaker 1>What happens is the sound causes an air embolism within

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<v Speaker 1>your lungs that can travel to your heart and kill

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<v Speaker 1>you dead. That is, if your lungs don't burst first

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<v Speaker 1>from the increased air pressure caused by acoustic energy. This

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<v Speaker 1>is how happened during wars, when high energy impulse noise

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<v Speaker 1>from explosions causes something called blast over pressure. It leaves

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<v Speaker 1>no external injuries, but damages organs like your ears, lungs,

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<v Speaker 1>and gastro intestinal tract. Now, acoustic weapons are actually being developed,

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<v Speaker 1>but usually there for non lethal purposes. There's been talk

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<v Speaker 1>of acoustic bullets to burst ear drums, incapacitate a target,

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<v Speaker 1>or even kill them. Others claim that an infrasound generator

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<v Speaker 1>could also be lethal, but there's been little practical evidence

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<v Speaker 1>of such weapons so far. The closest we've seen is

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<v Speaker 1>a long range acoustic hailing device developed by the l

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<v Speaker 1>Rad Corporation, which can cause hearing damage from up to

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<v Speaker 1>fifty feet or fifteen point two four meters away. Some

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<v Speaker 1>shipping companies have started using these devices as seaborne defense

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<v Speaker 1>against pirates. There is one device, however, that could most

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<v Speaker 1>definitely kill you with sound. It's not a weapon, but

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<v Speaker 1>the European Space Agency has developed a huge air horn

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<v Speaker 1>that they used to test satellites and spacecraft, using nitrogen

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<v Speaker 1>gas to produce sounds up to one hundred and fifty

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<v Speaker 1>four decibels. They blast objects to make sure they can

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<v Speaker 1>withstand the noise of a rocket launching. The e s

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<v Speaker 1>A themselves are so concerned about how lethal this horn

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<v Speaker 1>is they've surrounded it with half meter thick walls made

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<v Speaker 1>of steel reinforced concrete coated with an epoxy resin to

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<v Speaker 1>reflect noise back into its chamber. But Christian, you're asking,

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<v Speaker 1>didn't you just say that the threshold for death is

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<v Speaker 1>between one hundred and eighty five and two hundred decibels.

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<v Speaker 1>It's true I did, but the E s A believe

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<v Speaker 1>that prolonged exposure to the one hundred and fifty four

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<v Speaker 1>decibel horn will kill you as well, probably rupturing your

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<v Speaker 1>ear drums, vibrating your eyeballs, and destroying you from the

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<v Speaker 1>inside out. If you're not dead, you'll probably wish you were.

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<v Speaker 1>Check out the brainstuff channel on YouTube, and for more

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<v Speaker 1>on this and thousands of other topics, visit how stuff

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<v Speaker 1>works dot com.